1. Field of the Invention
This invention relates to rotating electrical permanent magnet machines, and more particularly to a stator assembly for an electrical machine.
2. Description of the Prior Art
Thermal characteristics play an important part in the operation of motors and generators because temperature rise limits a machine's rating and therefore its applications. Temperature rise in an electrical machine is caused by the heat produced by various energy losses. One source of energy loss (and therefore temperature rise) is the stator iron. In general, the primary purpose for the stator iron is to reduce the reluctance of the magnetic circuit to obtain acceptable excitation losses. A secondary purpose is to position and support the stator conductors. Unfortunately, this results in enclosure of the conductors so that they are not directly exposed to the flow of cooling air. Thus the stator iron causes stator temperature to rise by interference with heat transfer and by contributing to the heat in the stator.